Re: [PATCH] powerpc/powernv/idle: Restore IAMR after idle

[Russell Currey <ruscur@russell.cc>]

On Thu, 2019-02-07 at 15:29 +1100, Michael Ellerman wrote:
> Russell Currey <ruscur@russell.cc> writes:
> > 
> > Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of
> > user
> > space")
> 
> Don't word wrap the fixes line please.

My bad, will teach my editor :)

> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > ---
> >  arch/powerpc/include/asm/cpuidle.h |  1 +
> >  arch/powerpc/kernel/asm-offsets.c  |  1 +
> >  arch/powerpc/kernel/idle_book3s.S  | 20 ++++++++++++++++++++
> >  3 files changed, 22 insertions(+)
> > 
> > diff --git a/arch/powerpc/include/asm/cpuidle.h
> > b/arch/powerpc/include/asm/cpuidle.h
> > index 43e5f31fe64d..ad67dbe59498 100644
> > --- a/arch/powerpc/include/asm/cpuidle.h
> > +++ b/arch/powerpc/include/asm/cpuidle.h
> > @@ -77,6 +77,7 @@ struct stop_sprs {
> >  	u64 mmcr1;
> >  	u64 mmcr2;
> >  	u64 mmcra;
> > +	u64 iamr;
> >  };
> 
> We don't actually need to put this in the paca anymore.
> 
> > diff --git a/arch/powerpc/kernel/idle_book3s.S
> > b/arch/powerpc/kernel/idle_book3s.S
> > index 7f5ac2e8581b..bb4f552f6c7e 100644
> > --- a/arch/powerpc/kernel/idle_book3s.S
> > +++ b/arch/powerpc/kernel/idle_book3s.S
> > @@ -200,6 +200,12 @@ pnv_powersave_common:
> >  	/* Continue saving state */
> >  	SAVE_GPR(2, r1)
> >  	SAVE_NVGPRS(r1)
> > +
> > +BEGIN_FTR_SECTION
> > +	mfspr	r5, SPRN_IAMR
> > +	std	r5, STOP_IAMR(r13)
> > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
> 
> We have space for a full pt_regs on the stack, and we're not using it
> all.
> 
> We don't have a specific slot for the IAMR (we may want to in
> future),
> but for now you could follow the time-honoured tradition of (ab)using
> the _DAR slot, with an appropriate comment.

I read this, then did it, and when writing the comment I thought I was
clever using "(ab)use".  I then reread this and realised I just
subconsciously stole it.

Thanks for the review.

> cheers